#include <iostream>
#include <cstdio>

using namespace std;

int main()
{
    int a, b, c;
    cin >> a >> b >> c;
    if (a == b)
    {
        cout << "C";
        return 0;
    }
    if (b == c)
    {
        cout << "A";
        return 0;
    }
    if (a == c)
    {
        cout << "B";
        return 0;
    }
}